Medium time allocation and scheduling using iso-zone structured superframe for QoS provisioning in wireless networks

ABSTRACT

Allocation of contiguous blocks of airtime for data or airtime transmission can lead to large maximum service intervals for an application stream. This may result in a large delay bound where large blocks of contiguous MAS blocks other applications from meeting their low-latency requirements. A method and network that overcomes at least the shortcomings of known methods includes transmitting information over a wireless network. This includes the steps of: organizing the shared medium into periodical superframes; organizing the superframe into allocation zones; organizing the allocation zones into iso-zones; generating an allocation map; determining a periodic service interval and medium time based on a TSPEC including a latency requirement of an application stream, and local resource of the transmitting device; searching for transmission opportunity that accommodates the periodic service interval and the medium time required based on the allocation map; transmitting information in the superframe upon finding transmission opportunity in the searching step.

This Application claims the benefit of priority from prior U.S.application 60/674,495, filed Apr. 25, 2005, the teachings of which areherein incorporated by reference.

The wireless communication bandwidth has significantly increased withadvances of channel modulation techniques, making the wireless medium aviable alternative to wired and optical fiber solutions. As such, theuse of wireless connectivity in data and voice communications continuesto increase. These devices include mobile telephones, portable computersin wireless networks (e.g., wireless local area networks (WLANS), aswell as audio/visual streaming, video/audio telephony, stationarycomputers in wireless networks, and portable handsets, to name only afew).

Each wireless network includes a number of layers and sub-layers, suchas the Medium Access Control (MAC) sub-layer and the Physical (PHY)layer. The MAC layer is the lower of two sublayers of the Data Linklayer in the Open System Interconnection (OSI) stack. The MAC layerprovides coordination between many users that require simultaneousaccess to the same wireless medium.

The MAC layer protocol includes a number of rules governing the accessto the broadcast medium that is shared by the users within the network.As is known, several different multiple access technologies (oftenreferred to as MAC protocols) have been defined to work within theprotocols that govern the MAC layer. These include, but are not limited,to Carrier Sensing Multiple Access (CSMA), Frequency Division MultipleAccess (FDMA) and Time Division Multiple Access (TDMA).

While standards and protocols have provided for significant improvementin the control of data traffic, the continued increase in the demand fornetwork access at increased channel rates while supportingquality-of-service (QoS) requirements for multimedia traffic such asvoice or video have required a continuous evaluation of protocols andstandards and changes thereto. For example, many known protocols such asthe WiMedia Ultra-Wide Band (UWB) MAC 1.0 (published as ECMA standard368) and other non-slot based WLANs such as IEEE 802.11e, requirenetwork-layer QoS signaling protocols to pass QoS requirements ofapplications to network nodes along the path the applications traversein the form of Traffic Specification (TSPEC). The Station ManagementEntity (SME) located in each of such network nodes passes down the TSPECit receives to MAC Layer Management Entity (MLME). Upon receiving theTSPEC of the application stream, the MLME in MAC layer reservesnetworking resources to meet the QoS requirements. In various MACprotocols, one such resource is the medium time, or airtime fortransmission of data or other information. QoS provisioning in thesewireless MAC protocols usually involves allocation of airtime accordingto a QoS requirement specified, for example, in the TSPEC. For example,in slot-based MAC protocol, such as the WiMedia UWB MAC, there arevarious ways to allocate media access slot (MAS) (e.g., medium accesstime) that result in performance differences in latency, bandwidthefficiency, power saving performance, etc.

Contiguous medium time allocation is usually preferred to maximizebandwidth efficiency as well as power efficiency. However, Allocation ofcontiguous blocks of airtime for data transmission can lead to largemaximum service intervals for an application stream. This may result ina large latency where large blocks of contiguous airtime is likely toblock other applications from meeting their low-latency requirements.Additionally, too many smaller distributed fragments of airtimeallocation over the course of a superframe may also not enablesuccessful transmission of an entire packet, therefore results in lowerbandwidth efficiency

What is needed, therefore, is a method and system that substantiallyovercomes at least the shortcomings of known methods described and as aresult, to accommodate applications with various QoS requirements suchas high-efficiency and low-latency, to coexist

In accordance with an example aspect, a method of transmittinginformation over a wireless network includes the steps of: organizingthe superframe into a plurality of allocation zones; organizing theallocation zones into iso-zones; generating an allocation map;determining a periodic service interval based on a TSPEC including alatency requirement of an application stream, and local resource of thetransmitting device; determining a medium time requirement based on theTSPEC including a latency requirement of an application, and localresource of the transmitting device; searching for transmissionopportunity that accommodates the periodic service interval and themedium time required based on the allocation map; transmittinginformation in the superframe upon finding transmission opportunity inthe searching step.

The invention is best understood from the following detailed descriptionwhen read with the accompanying drawing figures. It is emphasized thatthe various features are not necessarily drawn to scale. In fact, thedimensions may be arbitrarily increased or decreased for clarity ofdiscussion.

FIG. 1 is a diagram representative of wireless communication networksystem sharing a medium in accordance with an example embodiment;

FIG. 2 is a time-line of a superframe in accordance with an exampleembodiment;

FIG. 3 is a two dimensional representation of a superframe;

FIG. 4 is a flow chart depicting a method of organizing iso-zones;

FIG. 5 is a flow chart depicting a method of generating an allocationmap; and

FIG. 6 is a flow chart depicting a method of transmission of informationover a wireless network according to the invention;

FIG. 7 is two dimensional representation of a superframe with apartially occupied beacon zone.

FIG. 8 is a flowchart of a computer program for generating an allocationmap.

In the following detailed description, for purposes of explanation andnot limitation, example embodiments disclosing specific details are setforth in order to provide a thorough understanding of the exampleembodiments. However, it will be apparent to one having ordinary skillin the art having had the benefit of the present disclosure that otherembodiments that depart from the specific details disclosed herein.Moreover, descriptions of well-known devices, methods, systems andprotocols may be omitted so as to not obscure the description of thepresent invention. Nonetheless, such devices, methods, systems andprotocols that are within the purview of one of ordinary skill in theart may be used in accordance with the example embodiments. Finally,wherever practical, like reference numerals refer to like features.

Briefly, in accordance with illustrative embodiments, methods and systemare described that improve the efficiency and throughput in adistributed wireless network while satisfying wide-range latencyrequirements from various applications. The methods and system calculatethe maximum service interval that will meet the TSPEC including latencyrequirement of one or more application streams. This is accomplished,for example, by organization of wireless medium into periodicaliso-zones; searching for transmission opportunity in the ascending orderof iso-zone indices; and by allocating contiguous MAS (i.e., portions ofmedia access time) to minimize power loss due to numerous “wake-up”operations.

In accordance with the example embodiments described herein, distributed(i.e., slot-based) wireless networks operate under WiMedia MAC 1.0. Ofcourse, this is merely illustrative, and other MAC protocols mayincorporate the sharing of availability of the devices within thenetwork that are described in connection with the example embodiments.These include, but are not limited to, the progeny of the currentWiMedia MAC protocol, as well as other carrier sense multiple accesswith collision avoidance (CSMA/CA) protocols or Time Division MultipleAccess (TDMA) protocols. Additionally, the embodiments described hereinmay also apply to WLANs having non-slot based media access, such as IEEE802.11 WLAN. It is emphasized that these protocols are merelyillustrative and that other protocols within purview of one of ordinaryskill in the art may be implemented in accordance with the exampleembodiments.

FIG. 1 is a schematic diagram of a wireless network system that includesplurality of wireless devices or systems sharing a communications medium(i.e., co-existing) in accordance with an example embodiment. Wirelessdevices/systems 101 may transmit or receive (or both) traffic 104 tofrom other wireless devices 101 within their transmission range 102.Moreover, there may be other wireless devices/systems 103 that areoutside the range 102 of certain wireless devices/systems 101, butwithin the range of certain devices 101′. Wireless devices 101 contain atransceiver 110 (e.g., any known transmitter/receiver combination, or aseparate transmitter and receiver), a processors 111 (e.g., any knowndevice which processes bits of information), and a power source 112(e.g., a battery).

Wireless medium is first organized into periodical and contiguous piecescalled superframes. FIG. 2 is a time line 200 of a superframe between afirst beacon 201 and a second beacon 202. As used herein, the startingpoint of the beacons is referred to as the Beacon Period Start Time(BPST), and there is a prescribed period of time between beacons. In anexample embodiment, the superframe is divided into a plurality of mediumaccess slots (MAS) 203, which provide for organized transmission andreception in keeping with the example embodiments. In an illustrativeembodiment, there are 256 slots 203, with each slot having a duration ofapproximately 256 μs, so the entire duration of the superframe isapproximately 65.536 ms in the example embodiment (thus 65.536 msbetween BPSTs). Of course the number and duration of the slots 203 ismerely for purposes of illustration and are in no way limitations of theslots 203.

At the beginning of each superframe there is a beacon period 204. Aswill become clearer as the present description continues, the beaconperiod 204 provides the vehicle for the sharing of availabilityinformation of the devices/systems (e.g., devices 101, 103) of thenetwork 100, as well as the needs of devices/systems to send traffic toother devices/systems of the wireless network 100 of the exampleembodiments.

After the beacon period 204 is a data transfer period 206 that maycontain a plural of service intervals 205. In slot-based medium access,each data transfer period is further divided into a certain number ofmedium access slots. Different application streams require differentnumbers of slots 203 to ensure adequate medium access time for completepacket transmission. A processor in a transmitter determines how much ofthe medium time it requires to transmit its data packets. Thisdetermination occurs by analyzing TSPEC (of the application stream)including bandwidth requirements, latency requirements and packet sizesand other local resource such as buffer space of the transmittingdevice. Additionally, service intervals are periodic (i.e., occurringover several cycles of beacon period 204 and data transfer period 206,or simply a superframe).

To calculate the periodic service interval, a processor (e.g., processor111 in FIG. 1) calculates a service rate g according to a TSPEC andlocal resource, such as buffer space required to temporally storepackets when wireless medium or system processing resource isunavailable. The processor also calculates the queuing delay d_(q)caused by burstiness of the application stream (measured as burst sizefield in TSPEC) by using the calculated g at which the stream is served.The maximum service interval 205 can be calculated by based on thelatency requirement, for example, as follows:SI≦d _(s) −d _(q)where d_(s) is the delay requirement and d_(q) is the additional queuingdelay caused by the burst burstiness of the application stream.

FIG. 3 depicts a two-dimensional representation of superframe 200. They-axis of the representation is MAS increasing sequentially in timelinein the downward direction for slot based systems such as UWB ortransmission opportunity in medium progressing in timeline in thedownward direction for non-slot-based systems such as IEEE 802.11. Thex-axis of the representation is allocation zone that increasessequentially in timeline in the horizontal direction (i.e., from left toright on the figure). Allocation zones 1-15 represent a contiguousgrouping of transmission opportunity, for example, MAS. Sequentially intime, MAS where x=2 and y=1 follows MAS where x=1 and y=15. According tothe prior art, incoming application streams were pre-assigned either ahigh-efficiency scheme or a low-latency scheme, depending on QoSrequirements of the application specified in the form of TSPEC. In alow-latency scheme, data transmission occurs exclusively in MAS slots(e.g., row components) where x=1, y=15; x=2, y=15, . . . , x=15, y=15.4. For a high-efficiency scheme, contiguous MAS blocks are utilized.

In order that MAS are allocated accounting for both application serviceinterval requirements as well as reservations of contiguous blocks ofMAS, iso-zones 301-304 are organized to parse out transmissionopportunity in an efficient manner.

FIG. 4 depicts a method for parsing a superframe into allocation zones1-15. For non-slot based systems, such as 802.11e, a scheduler in a QoSaccess point (QAP) is responsible for scheduling medium access forapplication streams. First, in step 401, a scheduler determines theminimum service interval the wireless network can accommodate oraccording to all the service interval requirements of existingapplications streams. The scheduler then divides the duration of thesuperframe by the minimum service interval to generate a value z in step402. In step 403, the scheduler calculates the number of allocationzones to be 2^(m), within a superframe based on the formula:m=┌log₂z┐wherein the function ┌x┐ returns the smallest integer that is greater orequal to x. Thus the number of allocation zones depends on the durationof superframe and the minimum service interval of the existingapplications, or the types of applications the QoS access point (QAP)intends to support. The number of allocation zones n will be thesmallest power of 2 greater or equal to the division of the superframeduration and the minimum service interval to support.

For slot-based systems such as UWB, a superframe is organized intoallocation zones by subdividing (402) the superframe into 2^(m)contiguous pieces with equal durations, where m=(1, 2, 3, . . . ). Thisensures a power of 2 number of allocation zones which can be parsed outfor transmission opportunity. For example, the WiMedia UWB MAC 1.0 callsfor a 256 MAS superframe structured into 16 allocation zones (e.g., thex-axis of FIG. 3) and 16 row components (e.g., the y-axis of FIG. 3).

Regardless of whether the wireless transmission opportunity isslot-based or not, its superframe can be organized into a number ofallocation zones n which is a power of 2. The beacon period resides inthe first allocation zone (indexed by “0”), which is referred to asbeacon zone.

Once the superframe is parsed into allocation zones, in order toefficiently account for both application service interval requirementsas well as reservations of contiguous blocks of transmissionopportunity, the allocation zones are organized into an ordered list ofsets, called iso-zones each identified by an iso-zone index value. Theiso-zones have periodical service intervals that are multiples ofallocation zone duration. FIG. 3 depicts iso-zones with index values of3, 2, 1, and 0 (with m equal to 4).

As an illustration of the formation of iso-zones. FIG. 5 depicts a flowchart diagram for organizing a superframe's allocation zones intoiso-zones by a marking process. In step 501, an application marks afirst allocation zone after the beacon zone with an iso-zone index valueequal to m−1, e.g. 3. This can be allocation zone 1 in FIG. 3. In step502, the application decrements the iso-zone index value by 1 and marksa second subsequent allocation zone with the decremented iso-zone indexvalue. This can be allocation zone 2 in FIG. 3 which is assignediso-zone index value 2. The application then mirrors the iso-zone indexvalue of the first allocation zone in a third allocation zone withrespect to and subsequent to the second allocation zone in step 503. Anexample of this mirroring is to assign allocation zone 3 in FIG. 3 withthe same iso-zone index value as allocation zone 1. The mirroring refersto a mirror image iso-zone index values for the allocation zones 1 and 3on opposite sides of allocation zone 2 in FIG. 3.

In step 504, the process repeats whereby the steps of decrementing,marking, and mirroring continue. For example, in FIG. 3, allocation zone4 is assigned an iso-zone index value of 1 which is a decremented value.Then allocation zone 3,2 and 1 are used for the mirroring step andallocation zones 5, 6, and 7 are marked with the iso-zone index valuesof allocation zones 3, 2, and 1 respectively. This process continuesuntil step 505 determines that the marking step marks an allocation zonewith an iso-zone index value equal to 0. In FIG. 3, this is allocationzone 8. This is the midpoint of the superframe (without considering thebeacon zone in allocation zone 0). The application then performs anadditional iteration of mirroring and marking in step 506. For example,once allocation zone 8 in FIG. 3 is marked with an iso-zone index value0, mirroring takes place by marking allocation zones 9 through 15 withthe iso-zone index values of allocation zones 7 through 1, respectively.Marking need not be physical marking. Marking may be assigning bitsindicating the iso-zone index value of a particular allocation zone. Andthe goal of such mark process is to generate an ordered list of sets ofallocation zones, or iso-zones. Such an ordered list is calledallocation map.

Alternatively, the allocation map can be generated by a computer programwithout physical marking process, or computed manually in advance.

FIG. 8 depicts a flowchart of such program.

Table 1 depicts an allocation map that stores an ordered list of the isozone index, the number of zones the iso-zone comprises, periodicalservice interval and the allocation zones the iso-zone contains for eachiso-zone:

TABLE 1 Iso- zone Number of Native SI Index zones (k) (ms) AllocationZones 0 1 16 * 4.096  8 1 2 8 * 4.096 4, 12 2 4 4 * 4.096 2, 6, 10, 14 38 2 * 4.096 1, 3, 5, 7, 9, 11, 13, 15Once an allocation map is created, an application can search fortransmission opportunity within a superframe.

FIG. 6 depicts the method for transmission of information over awireless network. In step 601, an application organizes a superframeinto a plurality of allocation zones as recited above. In step 602, theapplication organizing the allocation zones into iso-zones as recitedabove. In step 603, the application generates an allocation map (forexample, table 1). In step 604, the application determines a periodicservice interval based on a TSPEC, a delay requirement, and localresource of an application stream as recited above. In step 605, theapplication determines its medium time requirement based on the TSPEC,the delay requirement, and local resource of an application stream asrecited above. In step 606, the application searches for transmissionopportunity that accommodates the periodic service interval and themedium time required based on the allocation map. Once the applicationdetects there is transmission opportunity available that satisfies itsperiod service interval and medium time requirements, it transmitsinformation in the superframe in step 607.

The search step 606 searches in ascending order from the lowest iso-zoneindex value for transmission opportunity for high-efficiency QoSrequirements of an application.

Step 606 of searching for transmission opportunity includes calculatinga number of allocation zones k corresponding to service intervalrequirements using the formula

$k = \lceil \frac{BP}{SI} \rceil$for low latency QoS requirements.Then, the application determines a starting iso-index value from whichthe searching should begin by using allocation map as a lookup tablebased on k value determined above. The searching starts in ascendingorder from the starting iso-zone index value for transmissionopportunity compliant with low latency requirements of an application.

Given the properties described above, the following principles maximizethe size of contiguous unallocated medium time, and hence maximize thechance to meet requirement for incoming QoS requests and meanwhilesatisfying the delay requirement of current request.

-   -   (a) Optimal schedules are the ones that always start with the        lower-indexed iso-zone before scheduling in higher-indexed        iso-zones.    -   (b) Optimal schedules are the ones that keep current allocation        as flat as possible within each iso-zone. This actually        indicates the following generalized Evenly Distributed MAS        policy (EDMA) within each iso-zone in slot based medium access.        i.e., each iso-zone allocation should not allocate more than        n/k+1 MAS in each allocation zone within an iso-zone, where k is        the number of allocation zones that the schedule is taking        within the iso-zone under consideration.        Additional allocation maps (a.k.a, look-up tables (with n=16        and 32) are shown in 2-Table 4.

TABLE 2 Extended isozone based allocation map for total number ofallocation zones (n) = 16 Iso- Req./Act. SI zone Number of (number ofAllocation Zone Index zones (k) zones) Map 0 1 16  8 1 2  8-15/8 4, 12 2(Partial) + 0 3 6-7/6 2, 8, 14 2 4 4-5/4 2, 6, 10, 14 3 (Partial) + 1 63 1, 4, 7, 9, 12, 15 3 8 2 1, 3, 5, 7, 9, 11, 13, 15 3 + 2 + 1 + 0 151/1, 2 All

TABLE 3 Extended isozone based allocation map for total number ofallocation zones (n) = 32 Iso- Req./Act. SI zone Number of (number ofAllocation Zone Index zones (k) zones) Map 0 1 32  16 1 2 16-31/16 8, 242 (Partial) + 0 3 12-15/12 4, 16, 28 2 4 8-11/8 4, 12, 20, 28 3(Partial) + 1 6 6, 7/6 2, 8, 14, 18, 24, 30 3 8 4, 5/4 2, 6, 10, 14, 18,22, 26, 30 4(Partial) + 1 12 3 1, 4, 7, 9, 12, 15, 17, 20, 23, 25, 28,31 4 16 2 1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 4 +3 + 31 1/1, 2 All 2 + 1 + 0

TABLE 4 Efficiency-optimised extended isozone based allocation map fortotal number of allocation zones (n) = 32 Iso- Req./Act. SI zone Numberof (number of Allocation Zone Index zones (k) zones) Map 0 1 32  16 1 216-31/16 8, 24 2-Partial + 0 3 12-15/12 4, 16, 28 4, 3-Partial + 0 3 11 5, 16, 26/6, 16, 27 2 4 8-10/8 4, 12, 20, 28 {4, 3}-Partial + 5 7 2, 9,16, 23, 30 0 3 (Partial) + 1 6 6 2, 8, 14, 18, 24, 30 {4, 3}Partial + 75 2, 6, 11, 16, 21, 26, 30 0 3 8 4 2, 6, 10, 14, 18, 22, 26, 30 {4 ,3,2}Partial + 11 3 1, 4, 7, 10, 13, 16, 19, 22, 0 25, 28, 31 4(Partial) +1 12 3 1, 4, 7, 9, 12, 15, 17, 20, 23, 25, 28, 31 4 16 2 1, 3, 5, 7, 9,11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31 4 + 3 + 31 1/1, 2 All 2 + 1 +0

FIG. 7 depicts an iso-zone structure with a partially occupied beaconzone.

The iso-zone structure formed this way has the following properties:

-   -   1. Iso-zone i comprises 2′ allocation zones    -   2. Since

${{2^{m} - 1} = {\sum\limits_{i = 0}^{m - 1}2^{i}}},$the iso-zone structure is therefore complete in the sense that thesuperframe is completely covered by m iso-zones formed this way withoutany missing allocation zones, nor overlapping.

-   -   3. SI(i)<SI(i), ∀k>i; where SI(i) denotes the native service        interval that iso-zone i supports. This property indicates that        if iso-zone(i) meets the application's delay requirement, so        will iso-zone(k), ∀k>i.    -   4. SI({k,i})<SI(k), ∀k>i; where SI({k,i}) denotes the maximum        service interval achieved by allocation in iso-zone i in        additional to iso-zone k. This property indicates that if        iso-zone k meets the application's delay requirement, additional        allocation in any iso-zone(s) will not increase the worst-case        delay.    -   5. Native service interval of iso-zone i can be achieved in        iso-zone k, ∀k>i;

Example Algorithm for High-Efficiency Qos Requirements:

At the stage of determining the location of medium time,high-efficiency-low-power QoS requirements are already interpreted asthe number of allocation zones n(e) (that is a function of efficiencyfactor e) in addition to bandwidth requirement in the form of mediumtime duration/or size t(g) (that is a function of service rate g). Giventhe requirement input of {t(g), n(e)}, the following algorithmmaximizing the probability of satisfying the QoS requests for succeedingallocations while minimizing the number of allocation zones that theschedule takes to allocate medium time t(g):

1. Calculate unallocated medium time in all the allocation zones, i.e.

${n = {\sum\limits_{i = 1}^{z}{{unallocatedMediumTime}\mspace{11mu}( {{allocationzone}\lbrack i\rbrack} )}}},$

2. If (n≧t(g)), allocate t(g) according to policy (a) starting withiso-zone 0;

3. Within each iso-zone, follow policy (b)

4. Otherwise, report error of insufficient medium time.

For non-slot based systems such as IEEE 802.11, once the location isdetermined, the scheduler that resides in a QAP or QSTA may schedule thetraffic stream according the location determined this way together withthe duration determined by algorithms/mechanisms

In view of this disclosure it is noted that the various methods anddevices described herein can be implemented in hardware and softwareknown to achieve efficient medium access and sharing in a distributedwireless network. Further, the various methods and parameters areincluded by way of example only and not in any limiting sense. In viewof this disclosure, those skilled in the art can implement the variousexample devices and methods in determining their own techniques andneeded equipment to effect these techniques, while remaining within thescope of the appended claims.

In view of this disclosure it is noted that the various methods anddevices described herein can be implemented in hardware and softwareknown to achieve efficient medium access and sharing in a distributedwireless network. Further, the various methods and parameters areincluded by way of example only and not in any limiting sense. In viewof this disclosure, those skilled in the art can implement the variousexample devices and methods in determining their own techniques andneeded equipment to effect these techniques, while remaining within thescope of the appended claims.

1. A method of transmission of information over a wireless networkcomprising: organizing a wireless medium into periodical superframes;organizing the superframe into a plurality of allocation zones;organizing the allocation zones into iso-zones; generating an allocationmap; determining a maximum periodic service interval based on a TrafficSpecification (TSPEC) including a latency requirement of an applicationstream, and local resource of a transmitting device; determining amedium time requirement based on the TSPEC including a latencyrequirement of an application stream, and local resource of thetransmitting device; searching for transmission opportunity thataccommodates the maximum periodic service interval and the medium timerequired based on the allocation map; transmitting information in thesuperframe upon finding transmission opportunity in the searching step.2. The method of claim 1, wherein the step of organizing the superframeinto allocation zones further comprises: determining a minimum serviceinterval the wireless network can accommodate; dividing the duration ofthe superframe by the minimum service interval to generate a value x;determining the number of allocation zones to be 2^(m) based on aformulam=[log₂x] wherein the formula returns a smallest integer that is greateror equal to x.
 3. The method of claim 1, wherein the step of organizingthe superframe into allocation zones further comprises: dividing thesuperframe into 2^(m) allocation zones, where m=(1, 2, 3, . . . ). 4.The method of claim 1 wherein the step of organizing the allocationzones into iso-zones further comprises: marking a first allocation zonewith a iso-zone index value equal to m−1, where m=(1, 2, 3, . . . );decrement the iso-zone index value by 1; marking a second subsequentallocation zone with the decremented iso-zone index value; mirroring thefirst allocation zone in a third allocation zone subsequent to thesecond allocation zone; repeating the steps of decrementing, marking,and mirroring until the marking step marks an allocation zone with aniso-zone index value equal to 0; and performing one additional step ofmirroring and marking.
 5. The method of claim 4, wherein the mirroringstep further comprises replicating the iso-zone index value applied toeach allocation zones prior to an allocation zone marked in the markingstep in subsequent allocation zones that are subsequent to the markedallocation zone.
 6. The method of claim 1, wherein the allocation mapcomprises a table correlating the allocation zone with its markediso-zone index value.
 7. The method of claim 1, wherein the step ofsearching for transmission opportunity further comprises: searching inascending order starting from a lowest iso-zone index value fortransmission opportunity for high-efficiency QoS requirements of anapplication that does not have a latency requirement.
 8. The method ofclaim 1, wherein the step of searching for transmission opportunityfurther comprises: calculating a number of allocation zones kcorresponding to service interval requirements SI using the formula$k = \frac{BP}{SI}$ wherein BP is the duration of a superframe;determining a starting iso-index value from which the searching shouldbegin by looking up the allocation map with the k value; searching inascending order from the starting iso-zone index value for transmissionopportunity compliant with low latency requirements of an application.9. A wireless network comprising: a plurality of wireless devices, saidwireless devices each comprising: a transmitter for transmitting asignal; a receiver for receiving the signal; and a processor; and apower source; wherein the processor organizes a superframe into aplurality of allocation zones; organizes the allocation zones intoiso-zones; generates an allocation map; determines a maximum periodicservice interval based on a Traffic Specification (TSPEC), a delayrequirement, and local resource of an application stream; determines amedium time requirement based on the TSPEC, the delay requirement, andlocal resource of an application stream; searches for transmissionopportunity that accommodates the maximum periodic service interval andthe medium time required based on the allocation map; and directs thetransmitter to transmit information in the superframe upon findingtransmission opportunity in the searching step.